my @n = (-25, 14, 50, 20, -7, -8, -10);
my $max = 2**@n;
for (my $i = 0; $i < $max; ++$i) {
  my $sum = 0;
  $sum += $n[$_] for grep $i & 2**$_, 0 .. $#n;
  if ($sum == 0) {
    my ($bits, @used) = $i;
    while ($bits) {
      my $high_bit = int(log($bits)/log(2));
      push @used, $n[$high_bit];
      $bits &= ~(2**$high_bit);
    }
    print "[@used] = 0\n";
  }
}

##</code><code>##

my ($bits, $j, @used) = ($i, 0);
while ($bits) {
  push @used, $n[$j] if $bits & 1;
  $bits >>= 1, ++$j;
}

##</code><code>##

for (
  my ($bits, $j, @used) = ($i, 0);
  $bits;
  $bits >>= 1, ++$j
) {
  push @used, $n[$j] if $bits & 1;
}